Law started his apprenticeship with Chesterfield in 2005, before signing his first professional contract in July 2007. He made his first-team debut against Hartlepool United in the Football League Trophy in September 2007, seeing a shot cleared off the line and another hitting the bar.
He joined Conference North club Alfreton Town, managed by his father, on a three-month loan in October 2007. At the end of the loan, the deal was extended until the end of the 2007–08 season. After being released by Chesterfield upon the expiry of his contract, Law made a permanent move to Alfreton in the 2008 close season. After his first full season at the club, Law signed a one-year contract and then the following summer signed another one-year contract. During his time at the club, Law played in both full back and midfielder position. At the end of 2010–11, Law was given the Players' Player of the Season Award. He was also named in the 2010–11 Conference North Team of the Season. At the end of 2011–12, Law signed another one-year contract with the club. In May 2013, Law signed another one-year contract with the club. Law spent seven seasons at Alfreton and made over 250 appearances, where he was one of the longest serving players at the club at the time.
Motherwell
On 21 May 2014, Law completed a free transfer to Scottish Premiership club Motherwell, the same club his brother Nicky had played for previously, on a one-year contract. Law said he hoped the move to Motherwell would help him "establish myself in my own right and make a name for myself". Law made his first competitive appearance for Motherwell on 17 July 2014, in the UEFA Europa League second qualifying round first leg match against Stjarnan, in which he scored both Motherwell goals in a 2–2 draw at Fir Park. Law also played in the second leg, but Motherwell lost 3–2, being eliminated 5–4 on aggregate. Half-way through the season, Law changed role, moving into defence as a right-back, starting against Dundee on 10 January 2015. Law's performance soon earned him the club's Player of the Month award for February. In 2014–15, Law made 40 appearances, scoring twice. On 27 May 2015, Law signed a new two-year contract with Motherwell. Law played in both legs as a right-back against his brother, as Motherwell beat Rangers 6–1 on aggregate to stay in the Scottish Premiership.
Oldham Athletic
On 9 July 2016, having asked to leave Motherwell for family reasons, Law signed for League One club Oldham Athletic on a one-year contract. He scored his first goal for Oldham in a 2–1 EFL Cup win against Wigan Athletic on 9 August 2016. He was released at the end of 2016–17.
