ESPN reports that MLB will announce that they will suspend players for ten days if they find them with banned substances:

The league will distribute a memo to teams, which have been briefed on the broad strokes of the policy change, that outlines its plans to penalize all players caught by umpires with any foreign substance on their person, from the widely used sunscreen-and-rosin combination to Spider Tack, an industrial glue that has become a favorite among pitchers who want to generate more spin on the ball.

The liberal interpretation of Rules 3.01 and 6.02(c), which ban the use of foreign substances, would discipline all substances the same. While there is a “broad consensus among players that Spider Tack is over the line,” a high-ranking person on the players’ side told ESPN on Monday, the full ban of all grip agents could rankle players. A longtime umpire told ESPN the hard line is vital as he and his brethren attempt an on-the-fly enforcement of a rule that for years has been ignored.

ESPN.com

So this is going to be very interesting, as batters and pitchers both hurlers to get a good grip on the ball.

Multiple players said they were hopeful that MLB would differentiate among the substances and buy time before the potential issuance of a legal, universal substance pitchers can use for grip. While MLB has explored creating such a product, it has yet to formulate one that serves as a grip enhancer while not being a performance enhancer.

For now, rosin will have to do.