In front of the 4,512 fans, including 1,049 from Merseyside, who turned out to pay tribute to the Steelmen's left-back, Shane Duffy gave the visitors the lead in the 34th minute with a header which went in off the post.
However, midfielder Law levelled in the 54th minute with a left-footed drive from the edge of the box which gave Toffees keeper Tim Howard no chance.
A cameo substitute appearance by free agent James McFadden, who had played for both clubs, most recently being freed by the Goodison club at the end of last season, also entertained the crowd who watched a decent game played in the right spirit.
Hammell was given a guard of honour by both sets of players before the game.
The visitors had former Rangers duo Nikica Jelavic and Steven Naismith on the bench, the latter having yet to make his debut for the Merseysiders.
Motherwell struggled to get a kick in the early stages as Everton knocked the ball around for fun.
The visitors squandered a great chance in the 10th minute when Tim Cahill's cross from the left found Leon Osman, who bulleted a header from four yards high over the bar.
Moments later, Goodison striker Victor Anichebe ended a spell of pressure by flashing a drive from the edge of the box over the bar.
The home side, with trialist Simon Ramsden and youngster Adam Cummins in at centre-back due to injuries, responded.
Winger Chris Humphrey somehow got past Sylvain Distin to set up striker Michael Higdon, who also cleared the bar with a drive, before Law tested Howard who punched clear.
There was a moment of panic in the Everton defence when Motherwell wideman Jamie Murphy's driven cross from the left-hand side of the box was blocked by Howard but the Merseysiders reasserted themselves.
On the half-hour mark Darren Randolph dived low to his left to palm a Cahill drive past the post before the Australian headed Osman's corner over the bar.
Three minutes later, though, Everton were ahead when Duffy rose at the back post to head an Anichebe cross back across goal and in off the post.
Well started the second half better than they had the first, and Law had the Well fans on their feet when he lashed the ball high past Howard after the Everton defence had failed to clear a Tom Hateley cross.
Moments later, Higdon hit the outside of Howard's left-hand post with a drive after latching on to another Hateley cross.
Cummins came to Motherwell's rescue on the hour mark when he cleared a shot from Everton substitute Jack Rodwell, one of four changes made by David Moyes at the interval, off the line when it looked a certain goal.
McFadden got a huge cheer when he came on in the 62nd minute along with Fraser Kerr and Omar Daley, with Higdon, Murphy and Cummins making way.
In the 68th minute Naismith, to the jeers of the Well fans, came on to make his debut. John Heitinga was also introduced, with Distin and Marouane Fellaini going off.
Six minutes later McFadden combined with Henrik Ojamaa to set up Law but his drive went inches past the far post with Howard beaten.
Naismith was denied a debut goal in the 76th minute when Well substitute keeper Lee Hollis, on for Randolph at the break, blocked his close-range drive and Seamus Coleman failed to get the rebound on target.
Hateley stung the hands of Howard with a free-kick with four minutes remaining but there were to be no more goals before Hammell came on after the final whistle to take the acclaim of the fans.