There are many synonyms for the phrase "was in effect" that can be used to add variety and nuance to your writing. Some examples include: in force, operative, applicable, valid, active, in operation, underway, ongoing, functioning, established, prevailing, and operating. Each of these words carries its own connotations and implications, and can be chosen to convey a specific sense of meaning or tone. Experimenting with different synonyms can help you refine your writing style and enhance the impact of your message. Remember to choose a synonym that accurately reflects the intended meaning and fits the context of your sentence.