Come on, even knowing this, you have to admit there's probably a lot more unsolicited than solicited ones...
But they can be more judicious with whom they share contact details, and use the block button. They are not forced to be the recipient of any message.
Do you think the only solution is for a government backdoor?
They are the ones in power, not you & I.
Yeah prosecution makes lives more difficult, it's rife for abuse (the recipient could fake evidence, the sender could claim he was hacked/his friend took his unlocked phone..)..