Section 30610 shall not apply to the possession of a .50 BMG rifle, which was not defined or specified as an assault weapon pursuant to the then-applicable version of the former Chapter 2.3 (commencing with Section 12275) of Title 2 of Part 4 that was added to this code by Section 3 of Chapter 19 of the Statutes of 1989, by any person prior to May 1, 2006, if all of the following are applicable:

1. (a) At the time of the possession in question, the person was eligible under the then-applicable version of former Chapter 2.3 (commencing with Section 12275) of Title 2 of Part 4 to register that .50 BMG rifle.
2. (b) The person lawfully possessed the .50 BMG rifle prior to January 1, 2005.
3. (c) At the time of the possession in question, the person was otherwise in compliance with the then-applicable version of former Chapter 2.3 (commencing with Section 12275) of Title 2 of Part 4.