The case that immediately comes to mind involves an inquiry by the Senate Blue Ribbon committee in 1988-89. In that case (Bengzon vs. Senate Blue Ribbon Committee), the SC said that the contemplated inquiry in not in aid of legislation.

It is true that the power to conduct an inquiry in aid of legislation is co-extensive with the power to legislate. However, not all inquiries conducted pursuant to the oversight functions of Congress are considered in aid of legislation. This is gleaned from the disquition of Justice Puno in the 2003 case of Macalintal vs. COMELEC. See further discussion in the comment immediately below.
I believe that the SC did not lay the basis fo future gagging. With respect to Sec. 2 (a) of E.O. 464, the SC noted that it is merely an expression of opinion on the part of the President and this opinion is not conclusive or binding on other branches of the government. If Congress wants to use Sec. 21, it must lay the basis, veer away from Bengzon, and insist in enforcing the subpoena (in my humble opinion). This is in theory, of course, and I know that actual application is an entirely different matter.

By the way, Dean, thank you for the link. This site will host the purely legal stuff, with the lighter version still at the other site.

In your opinion, what activities of Congress are NOT in aid of legislation? For example, are oversight functions NOT in aid of legislation?

The “balancing of interests” technique that is redolent in the Decision, really centers around a distinction that the Court has seen fit to make between the Congress power of inquiry in aid of legislation which is located in Article VI Section 21, and the power of inquiry in the discharge of its oversight duty, in Section 22.

Following the Decision’s own avowed practice of construing government issuances in a manner that makes them Constitutional, I shall hope that the following quotation from Senate v. Ermita itself will apply in the coming controversies over it. Justice Carpio Morales says of the Arnault case –

The power of inquiry, the Court therein ruled, is co-extensive with the power to legislate. The matters which may be a proper subject of legislation and those which may be a proper subject of investigation are one. It follows that the operation of government, being a legitimate subject for legislation, is a proper subject for investigation.

By making the distinction that attendance at inquiries in aid of legislation is mandatory while that at inquiries of overshight are discretionary, and then accepting Section 2(a) in toto as having “no infirmity,” has not the Supreme Court merely laid the basis for future exercises of gagging government officials, especially the highest level ones. For like the “chilling effect” of Proclamation 1017 on media, the pusillanimous in the government services, or those merely vulnerable to the pressures of higher authority, have already received the signal to observe omerta in all things. Mike Defensor was right, EO 464 has already “served its purpose.”

It seems to me that the 1987 Constitution is confused about this one (or maybe I am)–because I think Sections 22 and 23 have set up a false distinction.

http://www.google.com/search?ie=UTF-8&oe=UTF-8&q=eo+464&btnG=Google+it%21&domains=http%3A%2F%2Fphilippinecommentary.blogspot.com%2F&sitesearch=http%3A%2F%2Fphilippinecommentary.blogspot.com%2F

(I’ve Linked your new website to Philippine Commentary)