Awful legislative drafting caused a 5 – 4 split in the United States Supreme Court in Corley v United States  No 07-10441, 6 April 2009.
The peculiarity of the legislation makes the case of little interest outside the USA but the difference between the majority (delivered by Souter J, joined by Stevens, Kennedy, Ginsburg and Breyer JJ) and the minority (delivered by Alito J, joined by Roberts CJ, Scalia and Thomas JJ) judgments reflects differing approaches to the significance of the context of a subsection.
Before looking at the details, I can summarise the broad position of the majority as being that the subsection (c) could not be read down to accommodate the wider meaning to be given to subsection (a). There was no legislative suggestion that (a) had to be the dominant provision, and in any event they dealt with different topics.
The case is about whether delay in bringing the accused before a court meant that his confession was inadmissible even though it was voluntarily made.
The first part of the legislation, 18 USC §3501(a), provides:
"In any criminal prosecution brought by the United States or by the District of Columbia, a confession, as defined in subsection (e) hereof, shall be admissible in evidence if it is voluntarily given. Before such confession is received in evidence, the trial judge shall, out of the presence of the jury, determine any issue as to voluntariness. If the trial judge determines that the confession was voluntarily made it shall be admitted in evidence and the trial judge shall permit the jury to hear relevant evidence on the issue of voluntariness and shall instruct the jury to give such weight to the confession as the jury feels it deserves under all the circumstances."
Note that this does not refer to the other subsections in §3501. Also, it only deals with voluntariness.
The minority treat this as the dominant provision, so that delay does not matter if the confession is voluntary.
The part of the legislation dealing with delay is §3501(c):
"In any criminal prosecution by the United States or by the District of Columbia, a confession made or given by a person who is a defendant therein, while such person was under arrest or other detention in the custody of any law-enforcement officer or law-enforcement agency, shall not be inadmissible solely because of delay in bringing such person before a magistrate judge or other officer empowered to commit persons charged with offenses against the laws of the United States or of the District of Columbia if such confession is found by the trial judge to have been made voluntarily and if the weight to be given the confession is left to the jury and if such confession was made or given by such person within six hours immediately following his arrest or other detention: Provided, That the time limitation contained in this subsection shall not apply in any case in which the delay in bringing such person before such magistrate judge or other officer beyond such six-hour period is found by the trial judge to be reasonable considering the means of transportation and the distance to be traveled to the nearest available such magistrate judge or other officer."
Note that this is a rule drafted in the negative, when it is, if read with the proviso, more sensible as a positive rule of exclusion. In effect it means a statement made after six hours of arrest or detention is inadmissible, provided that a longer time may not render the confession inadmissible if it was reasonable in the light of travel practicalities. That is how the majority interpreted it.
The minority reasoned that the admission of confessions made within six hours did not justify the implication that those made after longer delay were to be excluded.
The majority held that the minority's reading rendered subsection (c) redundant, or, as it said, "nonsensical and superfluous". The interpretative canon is that
" '[a] statute should be construed so that effect is given to all its provisions, so that no part will be inoperative or superfluous, void or insignificant . . . .' " Hibbs v. Winn, 542 U. S. 88, 101 (2004) (quoting 2A N. Singer, Statutes and Statutory Construction §46.06, pp.181–186 (rev. 6th ed. 2000))."
The majority pointed out that the minority were not reading the section as a whole, and to say that (a) is clear on its own proves nothing. The minority treated subsection as if it said "a confession will not be treated as involuntary because of delay if ...", whereas the word is inadmissible, not involuntary. Voluntariness and admissibility are not synonymous and both concepts are used in subsection (3); their different usage is not to be treated as simply a mistake in draftsmanship. They are different under the McNabb-Mallory rule at common law, which Congress is presumed to have been aware of:
Cannon v. University of Chicago, 441 U. S. 677, 699 (1979).
The majority reasoned that many evidential rules would be redundant if the only criterion for admissibility was voluntariness (the reduction ad absurdum argument), and that the legislative history supported its interpretation. The mischief of subsection (3) is interrogations of unlimited duration:
"No one with any smattering of the history of 20th-century dictatorships needs a lecture on the subject, and we understand the need even within our own system to take care against going too far. "[C]ustodial police interrogation, by its very nature, isolates and pressures the individual," Dickerson, 530 U. S., at 435, and there is mounting empirical evidence that these pressures can induce a frighteningly high percentage of people to confess to crimes they never committed, see, e.g., Drizin & Leo, The Problem of False Confessions in the Post-DNA World, 82 N. C. L. Rev. 891, 906–907 (2004).
"Justice Frankfurter's point in McNabb is as fresh as ever: "The history of liberty has largely been the history of observance of procedural safeguards." 318 U. S., at 347. McNabb-Mallory is one of them, and neither the text nor the history of §3501 makes out a case that Congress meant to do away with it."
So, illustrated here are various approaches to statutory interpretation: reading a provision in context, avoiding redundancy, reference to legislative intent, avoidance of absurdity. Another point was that established approaches should not be departed from, as here where the rule that relevant evidence is admissible (Rule 402, Federal Rules of Evidence) has been understood to be subject to exclusionary rules.