It is stipulated that the candidates for the MX2 category at the MXoN must be aged under-23 and the 19-year-old Lamont, 18-year-old Harwood and 22-year-old Carter each qualify on that score.
Reserve rider Carter will actually turn 23 just a few days after this year's MXoN.
Sponsored by BikesportNZ.com, Lamont has dominated the MX Development Under-19 class in Australia.
Tauranga-based Ben Townley was an automatic choice to race again this year but injuries had put him on the sideline until just a week or so ago and he is far from 100 per cent ready to return to this level of competition.
"The selection for the MX2 rider was always going to be difficult," said Townley, an experienced Motocross of Nations campaigner and winner of one of the MX1 class races the last time he raced the MXoN, in Denver, Colorado in 2010.
"I hope they start learning to love the feel of sand in the crack of their butt sooner rather than later."
New Zealand sent a "development squad" to the same event last season, when it was held in France, but none of those riders was considered this time around.
Though they fought bravely, last season's New Zealand development line-up of Auckland's Joel Doeksen (MX1), Elsthorpe's Kieran Scheele (MX3) and Rotorua's John Phillips (MX2) failed to qualify for the main event.
As a team, they finished 10th overall in the B final, a consolation race for non-qualifying countries, and ended the weekend with an overall Motocross of Nations ranking of 30th, beating just three of the 33 nations that had qualified to race that Sunday - Croatia, Lithuania and Iceland.
The United States trio won the event again last year, making it a seventh consecutive time that their representative team has topped the podium at the MXoN.
That win extended it to a record 22 times that Team USA has won the event outright since the MXoN was first staged, in Holland in 1947.
The American team for this year's event was also named in the past week and it comprises Ryan Dungey (MX1), Justin Barcia (MX3) and Blake Baggett (MX2). Dungey and Baggett were winning team members when the event was held in France last year.