No, I disagree to this statement.

Reasons : There are following exception to law of supply.

(i) Labour supply : In case of labour, as the wage rate rises, the supply of labour (number of hours of work) would rise. So the supply curve slopes upwards but the supply of labour decreases with a further rise in the wage rate, this is because the worker would prefer leisure to work after receiving higher amount of wages. Thus, after a certain point when wage rate rises the labour supply tends to fall.

(ii) Saving : Normally, when the rate of interest rises, saving increase. But some people want to have fixed regular income by the way of interest. They may save less at a higher rate of interest and savings tend to rise as the rate of interest falls.

(iii) Need for cash : If a seller is in urgent need of cash, he will supply a large amount of a commodity even at lower price.

(iv) Agricultural goods : The law of supply does not apply to agricultural goods as they are produced once a year and their production depends on climatic conditions. Due to unforeseen changes in weather, if the agriculture production is low, then this supply can't be increased even at a higher price.

(v) Future expectations about price : If a seller expects a fall in price in the near future, he will be willing to sell more, even at a lower price.

(vi) Rare Articles : Antiques artistic articles are exceptions to the law of supply because a change in price can't change their supply.