I think what you are asking, relates to the sale of toys, not ownership. The legal safety requirements would pertain to the ability of retailers selling certain products. If you privately import an item and don't resell it, the safety standards would not apply, and you shouldn't be worried about getting into trouble for owning toys that may or may not legally be sold in this country. If a toy is dangerously unsafe in some way, you would be liable for any injury it causes to others - but that would relate to anything you own, not just toys.
That said, I think our safety requirements aren't as bad as America, because we had the JP Masterpiece Ultra Magnus and MP Optimus with Trailer released here, which both had the long smokestacks. The American retailers seem to be the ones who can't sell Optimus with long smokestacks, and unfortunately, we end up getting the same thing in our Hasbro packaged toys.