Don't confuse assisted opening (AO) knives with automatic opening knives (switchblades). Switchblades are illegal in all fifty states. Assisted opening knives are legal in all fifty states with the exception of libtard places like New York city.
This link explains the differences better than I can.
http://aoknives.com/switchblades-vs-assistedAlso, there are different 'layers' of law on knives. Federal (mainly switchblades), state (definition of dangerous weapons), and local/city. There is no MN state law on length of pocket folders. There are city ordinances in both Minneapolis and St Paul. Both allow AO, and both limit the folder to four inch length blades.
Minneapolis, Minnesota, Code of Ordinances >> - CODE OF ORDINANCES >> Title 15 - OFFENSES—MISCELLANEOUS >> CHAPTER 393. - WEAPONS >> ARTICLE I. - GENERALLY
393.10. - Definitions.
Terms used in this chapter, unless expressly defined, shall have the meanings prescribed by the statutes of the State of Minnesota for the same terms. The following terms shall have the following meanings:
....
(f)
Weapon means any device designed as a weapon and capable of producing death, great bodily harm, or substantial bodily harm; or any other device or instrumentality which, in the manner it is used or intended to be used, is calculated or likely to produce death, great bodily harm, or substantial bodily harm, or the reasonable and immediate fear thereof. "Weapon" includes Chinese stars. "Weapon" does not include (1) except when used as a weapon, a folding knife with a blade of four (4) inches or less in length, measured in a straight line from the point to the handle; or (2) a firearm, unless expressly included by section 393.20(b). (Code 1960, As Amend., § 877.010; Ord. of 4-9-76, §§ 1, 2; 77-Or-221, § 1, 10-28-77; 85-Or-098, § 1, 5-10-85; 86-Or-149, § 1, 6-27-86; 87-Or-106, § 1, 6-12-87; 2007-Or-073, § 1, 10-5-07)
St. Paul, Minnesota, Code of Ordinances >> PART II - LEGISLATIVE CODE >> Title XXIII - PUBLIC HEALTH, SAFETY AND WELFARE >> Chapter 225. - Weapons
Sec. 225.01. - Definitions.
The following terms shall have the following meanings:
....
Knife shall mean dirk, dagger, stiletto, switchblade knife, spring blade knife, push button knife, a folding knife with a blade in excess of four (4) inches, a machete, a bayonet, or any fixed-blade knife, carried in a concealed manner or within reach of any person in a motor vehicle.
The two enemies of the people are criminals and government, so let us tie the second down with the chains of the Constitution so the second will not become the legalized version of the first.”
Thomas Jefferson