That staple of Denver Broncos football, veteran players sporting EAS baseball caps on the sideline and while mugging for the cameras, is probably gone for good.

In a crackdown that extends beyond normal drug testing and the recent ban of products containing the stimulant ephedra, the NFL and NFL Players Association agreed to prohibit players from endorsing companies that manufacture products on the league's list of banned substances.

The new policy, acknowledged NFLPA executive director Gene Upshaw, will be strictly enforced, and players have been apprised several times of potential consequences.

"It doesn't make sense for us to ban substances and then have players out there endorsing the companies that make the stuff," Upshaw said. "It doesn't send the right message. In fact, it's contradictory, we feel. We had to do something and we feel we are doing the right thing."

For years, Denver players such as linebacker Bill Romanowski and tight end Shannon Sharpe were shown on television wearing baseball caps bearing the logo of EAS, a Golden, Colo.-based manufacturer of dietary supplements. It is anticipated that, under the policy now in place, such public displays will cease.

Just this week, NFL officials began investigating Bills wide receiver Eric Moulds, whose endorsement of a bodybuilding supplement might violate the policy.

Moulds has been endorsing NITRO-Tech, a natural protein supplement that contains no ingredients on the NFL's banned substance list. But the manufacturer of NITRO-Tech, the Montreal-based company MuscleTech Research and Development, Inc., makes other supplements that contain components the NFL has banned.

The league has no concern with Moulds' endorsement of NITRO-Tech. At issue, though, is his endorsement of a MuscleTech-manufactured product. MuscleTech manufactures products that are banned by the league.

The company recently removed all mention of Moulds from its web site, and the standout wide receiver is exploring his options. If the NFL finds Moulds has violated the policy and he declines to remove his endorsement, he could be fined.

Moulds, who apparently was unaware some MuscleTech products were on the banned substance list, has said he wants to abide by league policy. It is believed the Moulds case is the first to be reviewed under the new policy.

Len Pasquarelli is a senior writer for ESPN.com.