The tactic is often discussed in the United States because under US law, unions are prohibited from talking with workers in the workplace and salting is one of the few legal strategies that allow union organizers to talk with workers. 
Non-union salts are called "peppers".
Ruling by the National Labor Relations BoardEdit
In Toering Elec. Co., 351 N.L.R.B. No. 18 (Sept. 29, 2007), the National Labor Relations Board (NLRB) concluded that workers can be fired if they are believed to not be "genuinely interested" in obtaining the job. This category includes salting.
"‘Salts’ try to destroy their employers," the anti-union National Right to Work Committee has written.