8:13 AM PT -- BOP tells TMZ that Todd and Julie actually could've communicated on Valentine's Day -- but they just had to get it approved and planned out beforehand. They also tell us inmates get their mail in a prompt timeframe, despite Todd's claims.

Todd and Julie Chrisley won't be sending their love to each other on Valentine's Day ... which their attorney says is coming as a huge drag.

The couple's attorney, Jay Surgent, tells TMZ the duo won't be able to communicate with one another on Valentine's Day 'cause inmates aren't permitted to get in touch while in different federal prisons.

You'll recall ... Todd was given a 12-year sentence at FPC Pensacola for a slew of fraud charges, while Julie was sent to FMC Lexington in Kentucky for 7 years -- so not only are they in separate prisons, but they're also in different states.

Their attorney tells us the Federal Bureau of Prisons has a no-crossover/contact policy... but Jay doesn't quite understand it, telling us it creates zero security problems or cause for concern.

Jay says the Chrisleys being unable to communicate during V-Day will be a real bummer ... especially cause their love for each other is unwavering and distance has only made the heart grow fonder.

Meanwhile, Jay says when he last spoke with Todd last week, TC said he wanted to pursue an investigation against FPC Pensacola prison administration for mail theft and general corruption ... among other things. He also claims he still hasn't received the mail he's been expecting, which raises further concerns with him.

As we all know by now, Todd's been vocal about the living conditions at his new digs ... ripping them apart for their disgusting food, possible mold, and bad plumbing.

But as it relates to the heart ... it seems like Todd and Julie's love is under lock and key for the time being.