AR-15s are already classified as assault weapons, and have been due years, unless they are "featureless", meaning none of the scary features. Come January 1st they will still be classified as assault weapons, unless featureless, but the law redefines one of the scary features: the magazine.

Previously, to avoid assault weapon requirements and registration, the law required a fixed magazine, which the bullet button satisfied. After January 1st it will require a non detachable magazine, which is defined as a magazine that is permanently affixed or requires disassembly of the action to remove, and existing rifles which no longer meet the featureless definition will have to be registered or disposed of.

Also, handguns are regulated under the assault weapons laws in a similar manner. Semi-automatic handguns which accept a non fixed magazine and have specific features are restricted. Come January 1st that definition now becomes a semi automatic handgun with a detachable magazine which means the same as above.

For more, including the list of banned features, see the text of SB-880.