[EricH]

Yes. If the electromagnet is causing the motion, then it is considered a solenoid actuator and illegal (<R53>). If anything else is causing the motion, and the electromagnet is acting as a latch, then the electromagnet is considered an electromagnet and legal.

As far as buying/making your own, you'd probably want to ask that in Q&A. It would probably wind up being answered as "both", but you never quite know.