Winger Josh Adams has been released by Wales after being suspended for the first two matches of the 2021 Six Nations following a breach of Covid-19 protocols.
The Cardiff Blues player, 25, attended a gathering with his immediate family present on Sunday, after the squad had been released from camp on Saturday.
The players linked back up on Tuesday and the breach was raised.
"I would like to apologise unreservedly," said Adams.
Adams made his international debut in 2018 and has scored 14 tries in 29 Tests for Wales.
He was expected to start in the tournament opener against Ireland on Sunday but will miss that game at the Principality Stadium and the trip to face Scotland six days later.
The latest round of Covid-19 testing results for the national squad all returned negative.
"When out of camp, at the weekend, I made an error of judgement," said Adams. "I attended a small gathering of immediate family to celebrate a family milestone.
"It was wrong to do this. I'm aware that everyone needs to follow the rules and, being in the public eye, I have a responsibility to lead by example and I've fallen short on this occasion.
"I'd like to apologise to my team-mates and to our supporters for my mistake."
'Everyone has a responsibility'
Wales head coach Wayne Pivac is already without suspended wing Liam Williams for the opening match, which kicks off at 15:00 GMT on Sunday.
Louis Rees-Zammit and George North are in contention for the wing berths to face Ireland, while Hallam Amos is another option.
The Wales squad recorded no Covid-19 cases during the two-month autumn campaign.
"It was dealt with pretty swiftly," said Pivac.
"It's breached team protocols, the Six Nations protocols and lockdown rules. We've been through a thorough education process with the players and the management. It put others at risk potentially so it was dealt with by way of suspension.
"We are extremely disappointed with the breach and have acted robustly and swiftly to take all appropriate measures.
"All players and management have received detailed briefings and education regarding our protocols, and everyone has a responsibility to abide by the rules.
"On this occasion, Josh has made an error of judgement. He made a mistake and he has shown immediate remorse.
"We will work with Josh in relation to his integration back into camp following a further testing and re-education process."
Adams will return to the Wales squad on Monday, 8 February if he is given the all-clear but will not be eligible for selection against Scotland five days later and will instead help the rest of the squad prepare.
Pivac explained how the incident had been discovered.
"It came to our attention yesterday after training and we spoke to the player and he was upfront and honest and realised the mistake he had made," said Pivac.
"It was just close family at a family member's home not too far from his own home, but it was in breach of the rules.
"It was a milestone which he's very proud of but unfortunately it is in breach of the rules.
"It was not a great distance and it was a very quiet celebration, as far as I'm aware.
"There was no alcohol involved. It was a celebration in terms of family members getting together for something special that's happened and we'll leave that to the family."
Pivac is confident the incident has not put the fixture in danger with close contacts not applying, as Adams has not tested positive or shown any symptoms. The Six Nations has been informed and backs the decision.
"We're now going through that process we've gone through, the ordinary testing that we do at the start of the week, and it's been 100% negative," added Pivac.
"The next stage is to get the second lot of testing done, which is already in place and if that comes through negative I think we're all in the clear."
Pivac was asked whether he would consider changing the policy of allowing the players to go home from the bubble during games.
"The message went out at the start of the competition about how we'd deal with any breaches," said Pivac.
"We've dealt with it how we said we would and that should be a lesson to everybody.
"You've got to treat these guys as adults, as they are, and as professional rugby players. It's a very long time to lock people away in a hotel.
"Everybody came back really refreshed, we had 100% negative results from our testing and have been very good apart from this one breach, which is unfortunate."