JUDGMENT

PUNCHHI, J.:- These four appeals by special leave are against the common judgment and order dated 3-4-1978 of the Judicial Commissioner of Goa, Daman & Diu in Special Civil Applications (Writ Petitions) Nos. 2/ 69, 12/ 69, 47 / 70 and 48 / 70 : (reported in 1978 Tax LR 2242). The Union of India and its officers are the common appellants herein.

2. Shortly put, the four writ petitioners before the Judicial Commissioner, the respondents herein, were carrying on mining operations in certain areas in the Union Territory of Goa, Daman and Diu. Thereat they had been using various types of mining machinery including dumpers and shovels. The Motor Vehicles Act, 1939 (hereafter referred to as the Act) was made applicable in the Union Territory w.e.f. 1-1-1965 and simultaneously the Motor Vehicles Taxation Act, 1965 (hereafter referred to as the Taxation Act) was also enforced on that date. The respondents claimed that being under a mistaken belief that their dumpers and shovels were motor vehicles and hence liable to tax under the Taxation Act, they initially got those registered under the Act and paid tax thereon under the Taxation Act. Later when they realised that they had paid ta