The Dallas Cowboys asked the NFL if the team could wear decals honoring the fallen members of the Dallas Police Department and the NFL, unsurprisingly, said no.

When training camp opened in Oxnard, Calif., earlier this offseason, the Cowboys unveiled "Arm in Arm" helmet decals, designed to pay tribute to the men who lost their lives during the downtown Dallas shooting in July, while also symbolically representing the Cowboys support of the community.

Naturally, the NFL won't let them wear the decals during the regular season.

"Everyone has to be uniform with the league and the other 31 teams," Jerry Jones said Wednesday. "We respect their decision."

It's pretty easy to get upset about the NFL over this. The league has a long history of appearing tone deaf when it comes to letting players and teams support various causes. Brandon Marshall, then with the Bears, was fined more than $10,000 for wearing green shoes to raise awareness for mental-health issues.

Steelers running back DeAngelo Williams wanted to wear pink all season long to honor his mother, who died of breast cancer. The NFL told him no.

But there is, as Jones pointed out, a "Pandora's box" issue at hand. If you let the Cowboys support fallen police officers, you've probably got to let Williams wear pink all season. And if you let him wear pink all season, you probably can't stop [Player X] from wearing [color] for [cause].

"There are so many wonderful, wonderful causes, the league has to be careful," Jones said earlier in camp about the possibility of wearing the decal in games. "If you allow one, then what do you do about every team that has a great reason to have something on their helmets?

"There are tons of things out there that need to be recognized. Once you open that Pandora's box, how do you ever stop?"

The NFL will allow teams to wear patches honoring people who were involved with the team -- the Patriots wore patches honoring Robert Kraft's late wife, Myra, during the 2011 season -- but is pretty strict with its stance about what is allowed in terms of charitable support. The Lions wore a patch to honor their late owner William Clay Ford during the 2014 season.

If the league won't change because of the Cowboys or because of Williams' mom (despite already having an entire month dedicated to breast cancer support), don't expect it to flinch on anything moving forward.