The answer to this question depends on the particular details of your employment agreement, the Stock Option Plan under which your options were issued, and the terms of any Stock Option Grant(s). The overall governing principle is that after a wrongful termination, you have a claim for damages for breach of contract, and the court should grant damages, in a lump sum, to compensate you fully for all losses. Full compensation means the lump sum should be enough to put you in the same position you would have been if you had been given working notice. During a working notice period, you would often continue to have options vest, and you would often have had a longer period of time to exercise any options.
Usually, but not always, Stock Option Plans state that employee stock options cease vesting on the date of actual (even wrongful dismissal) termination of employment, and the fired employee has a short period (usually 30 days) to exercise. The employee loses the ability to have additional options vest and to wait to exercise through a notice period. Damages should compensate for this.
Complicated mitigation issues arise as to whether the employee is obliged, in the 30 day “window”, to purchase the shares in respect of the options which had vested by then.
The general approach to damages discussed above (availability of damages for losses during the notice period) would likely not be appropriate, if the stock option benefit enjoyed by the employee was very clearly stated by the employment agreement, the Stock Option Plan and the Grant to expire if an individual’s employment ends even without notice and even if the termination was a wrongful dismissal. Clear language is required for this, however, and it is common for us to find a way to invalidate such language for a lack of clarity.