The ability to do that is HIGHLY restricted by labor laws. I'm not saying you couldn't get around it with very careful contracting... but I wouldn't want to count on it.
The ability to do that under the law is demonstrated by the fact that there are whole major industries where this kind of contracting with talent is normal. (Legal limitations tend to highly restrict the ability to get a remedy beyond money damages for breaches of such agreements, to be sure, but they don't tend to prevent the agreements themselves.)
It tends to be expensive (both in terms of what you pay the talent and in terms of the overhead associated with contracting), but if the talent is really valuable enough, that's the price you pay.
If you aren't willing to pay that price, you shouldn't complain about people "poaching" what you didn't want to pay the cost to have a durable claim to in the first place.
If your employees are under pure default at-will employment, its not poaching to seek to hire them out from under you, because you haven't purchased a property interest in their continuing to remain your employees. And, if you have purchased such an interest, then you suddenly don't need a no-poaching agreement to prevent them from being poached.
A multiparty no poaching agreement with the other main employers in the industry -- particularly a secret one -- is essentially trying to impose the restriction of having an extended contract with your employees without paying them for accepting that restriction.