The Employment Tribunal has rejected an age discrimination claim by lawyer Leslie Seldon against his former firm Clarkson Wright & Jakes (CWJ), which had initially seemed likely to threaten law firm's ability to enforce a compulsory retirement age for partners.

The ruling, made on Tuesday (28 May), ends a long-running battle between Seldon and his former firm, which began in an employment tribunal in 2007 when Seldon, who was ousted from CWJ's partnership in 2006 when he turned 65, argued that the firm's compulsory retirement age constituted age discrimination.

The case turned on whether age discrimination inherent in mandatory retirement policies can be justified under the law as a proportionate means of achieving a legitimate business aim, with CWJ arguing a list of six justifications, focused on making room for associates and junior partners to progress within the firm.

Seldon's claim had already been rejected by the Court of Appeal in 2011 and by the Supreme Court in 2012, when it was referred back to the Employment Tribunal to consider whether the retirement age of 65 was justified.

Tuesday's ruling by the Employment Tribunal though backs all of the previous decisions in favour of CWJ and seemingly offers more assurance for law firms seeking to justify their policies towards partner retirements. While many firms have raised partner retirement ages in response to age discrimination legislation, a large number have still opted to retain a default retirement age.

The Tribunal's ruling stated: "The lower the retirement age the more harm to the partners who are required to retire and the higher the retirement age the more harm to the associates who may leave.

"The age has to reflect the expectations of the partners and associates, ensure succession and fulfill the needs of the partnership."

Considering these two points the tribunal concluded: "In concluding that the age of 65 was proportionate the Tribunal has taken into account…that the partners had consented to the mandatory retirement age and that the default retirement age at the relevant time was 65. The Tribunal was support by the judgment of the Court of Appeal and its conclusion that a) the age of 65 was a fair and proportionate cut-off date in relation to the two aims and b) the selection of one of a number of possible ages was not of itself unlawful."

Related: Supreme Court rejects key challenge to partner retirement policies