He was ejected last Wednesday night against the Phillies and objected greatly to what was transpiring, as can be seen here.
The league announced on Tuesday that Smith was suspended:
Arizona Diamondbacks pitcher Caleb Smith has received a 10-game suspension and an undisclosed fine for possessing a foreign substance on his glove at the end of the eighth inning of his Club's Wednesday, August 18th game against the Philadelphia Phillies at Chase Field.
The league further announced that Smith has appealed the suspension, meaning the discipline will be held in abeyance until the appeals process is complete.
Smith, 30, has a 5.20 ERA and 1.42 WHIP with 110 strikeouts in 97 innings this season. Walks have been an issue, as he's issued 56.
By way of reminder, if Smith's suspension is upheld through the appeals process, the Diamondbacks won't be able to replace Smith's spot on the active roster.
This rule against using foreign substances by pitchers was on the books for decades, but things started to get out of control with pitchers going way too far while the league looked the other way these last several years. As a result, MLB issued a memo in the spring to ramp down the use of substances and that didn't work, so the league mandated that umpires would start checking pitchers on the field in late June. It was kind of a spectacle at first, but everyone seems to have gotten used to it by now.