He didn't, and he wouldn't. Ever.
Ron Paul was caught between the Tenth Amendment and the Second Amendment on the "gun lawsuits" issue. Ron Paul is certainly not in favor of the idiotic Gun Lawsuits, mind you, as he made clear in his Speech on the floor... but he believes (correctly, IMHO) that the Second Amendment applies to the Federal Congress, and that the Federal Congress has no right whatsoever to legislate on Guns one way or the other -- whether to Ban guns, or to tell the States how to run their business.
If Ron Paul had his way, the only Gun Laws would be those enacted by the States... and soon enough, New York and California would ban Guns entirely, while Texas would probably allow "open-carry" on the city streets.
Needless to say, New York and California would wither on the vine, while Texans would retain their Rights.
Ron Paul is okay with this. He does not support State restrictions on Guns, but in this case he went with the Tenth Amendment -- "Thou shalt not make a FEDERAL ISSUE out of a State's Rights question".
Congress has exclusive authority over interstate commerce; it was given such authority in part to prevent states from restricting it. Since these lawsuits are being filed precisely for the purpose of interfering with interstate commerce, I would think Congress should have the authority to ban them.
Also, per IV.1: "Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State. And the Congress may by general Laws prescribe the Manner in which such Acts, Records and Proceedings shall be proved, and the Effect thereof." What if Congress declares that judicial actions against gun manufacturers in other states shall be nullified?
The only problem with this is it creates an equal protection issue, along with the fact that the Second Amendment contains no limiting language similar to the First, i.e., "Congress shall make no law..."
Like it or not, nine of the amendments in the Bill of Rights have been "incorporated" so as to stand as a shield between a citizen and both the Federal and State governments. The Second Amendment has yet to undergo that anlaysis, but there is a line of legal theory that postulates that there is almost no prohibition to incorporation - and that the case for incorporation is stronger due to the underlying purpose of the Second (armed populace to keep government in line) and the lack of limiting language.
Add to the issue the interruption of interstate commerce through a purely state jurisdictional lawsuit and I believe Mr. Paul made the wrong call on this issue. (and I love the guy)