Both players have been on mandatory breaks following their summer commitments in South Africa, but they are now able to represent their club again.
It means there will be some interesting calls this week for Saints, who have won both of their Gallagher Premiership matches this season.
"Those two (Lawes and Biggar) can be considered for selection," Saints attack coach Sam Vesty confirmed.
Fraser Dingwall and Matt Proctor formed a strong centre partnership in the 26-24 win at Exeter Chiefs last Saturday.
But the likes of Piers Francis (shoulder) and Rory Hutchinson (neck) are on the comeback trail.
Vesty said: "We've got Piers Francis back training with us and he's still a little way off but he's back in being his tenacious self running around the pitch. It's good to have him back.
"Hutch picked up a little neck issue and it just needs a bit of time.
"While Dingers and Matty are doing a decent job, we're really happy we can have that time."
While new signings Juarno Augustus and Frank Lomani have been able to make their Saints debuts at the start of the season, the likes of Brandon Nansen, Karl Wilkins and Courtnall Skosan have yet to feature.
Wilkins has finished a ban carried over from his time in France last season, while Nansen is also in training.
Skosan has yet to arrive at Saints as he navigates the logistics of arriving from South Africa.
"Brandon and Karl and champing at the bit to get involved and get on the park," Vesty said.
"They're training really well and we can't wait for them to get out to play for us but they may be used elsewhere to get a little hit-out so that when they get their chance with us they're flying and ready to go.
"Courtnall is not at the club yet - he's doing some isolating - but he'll be here very shortly."