Kirtley, who was suspended in October last year after Tests showed his arm exceeding the permitted 15 degree flexion, worked under Sussex coaching staff last winter to rectify the problem.
Kirtley, who has played four Tests and 11 One-day internationals, passed a reassessment of his action at the ECB National Cricket Centre in Loughborough where he was given the green signal.
The Sussex website quoted ECB Umpires and Match Operations Manager Chris Kelly as saying, ''James has clearly worked hard and effectively during the winter with Mark Robinson, Professional Cricket Manager at Sussex, to remodel his action. When he was retested recently at Loughborough the level of elbow extension in James' action had reduced considerably and as the test results now fall within the prescribed tolerance levels, James is now free to bowl in County and international cricket.''
''At their pre-season meeting ECBs First Class Umpires will see footage of James remodelled action so that they are fully briefed on this issue,'' he said.
A relieved Kirtley said, ''I am delighted that the last five months of hard work has paid off - it has been an intense and emotional journey. I have received fantastic support from the Club and supporters, and I am particularly grateful to Mark Robinson and the Sussex coaching team for their tireless efforts.''
''I am now looking forward to taking an active role in the season, but understand the need to continue monitoring developments,'' he added.